669. Trim a Binary Search Tree

最新推荐文章于 2025-07-29 14:24:32 发布

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本文介绍了一种算法，用于修剪二叉搜索树，使其所有元素位于给定的最低和最高界限之间。通过递归地调整树结构，确保修剪后的树仍保持二叉搜索树的性质。

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Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.

Example 1:
Input: 
    1
   / \
  0   2

  L = 1
  R = 2

Output: 
    1
      \
       2
Example 2:
Input: 
    3
   / \
  0   4
   \
    2
   /
  1

  L = 1
  R = 3

Output: 
      3
     / 
   2   
  /
 1

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};


class Solution {
public:
    TreeNode* trimBST(TreeNode* root, int L, int R) {
        if(!root)
            return NULL;
        if(root->val < L)
            return trimBST(root->right, L, R);
        if(root->val > R)
            return trimBST(root->left, L, R);
        root->left = trimBST(root->left, L, R);
        root->right = trimBST(root->right, L, R);
        return root;

    }
};